Our objectives are to explore the relationships among immunostimulation, immunosuppression, virus activation, autoimmunity and oncogenesis in murine models and in man. Immunological activation of C-type oncornaviruses and cytomegaloviruses have been demonstrated in mice, and similar events are being explored in humans in post-transfusion mononucleosis, during pregnancy, and following renal transplantation. The ability of humans to mount cell-mediated responses against primate oncornaviruses is being examined. Studies of the efficacy of interferon prophylaxis in renal transplant recipients are underway. Cytomegalovirus-leukocyte interactions are being explored in vitro.